NR 518 Week 4 Study Design Comparison Example

Study Design Comparison: A Cohort Study or a Case-Control Study to Inform a County Decision on Wet-Cutting Requirements for Countertop Shops, Counted in People, Months and Access

Student Name

College of Nursing, Chamberlain University

NR 518: Population Health and Epidemiology in Nursing Practice

Instructor Name

Month Day, Year

Study Design Comparison: A Cohort Study or a Case-Control Study to Inform a County Decision on Wet-Cutting Requirements for Countertop Shops, Counted in People, Months and Access

The Decision

The county board of supervisors will decide within 18 months whether to fund a program requiring and subsidizing wet-cutting equipment and local exhaust ventilation in engineered stone countertop shops, paired with inspections. Board members have asked a fair question: is there local evidence that shops using wet methods have less silicosis? The county's practice screening data from Week 3 suggested a strong association but came from a one-time screening that cannot separate cause from other differences. This paper compares two study designs that could answer the question better and weighs them against the board's deadline.

Option A: A Prospective Cohort

Shape. Enroll workers without silicosis on a baseline CT, record each worker's cutting method and shop conditions, and repeat screening every two years to see who develops disease. Compare the rate of new silicosis in wet-cutting and dry-cutting workers.

What it would cost in people. Silicosis from engineered stone can appear after several years of exposure, and in the Week 3 practice data about 5% of wet-cutting workers already had disease. To detect a doubling of new cases with reasonable confidence, the county would need to follow several hundred workers in each group, and it would lose many to job changes and moves.

What it would cost in months. At least one repeat screening cycle, two years, before the first comparison, and realistically two or three cycles, four to six years, before the result is solid. That is well past the board's 18 months.

What it would cost in access. Every worker would need a CT every two years, with consent, time off work and follow-up for abnormal findings. Many workers in this industry are uninsured or have restricted coverage, and interviews with Los Angeles fabrication workers found that many feared being fired for raising safety concerns (Fazio et al., 2025). Keeping them in a multiyear study would require trust the county has not yet built.

What it would give. The strongest evidence of the two options: incidence measured forward in time, with exposure recorded before disease, so the order of cause and effect is clear.

Option B: A Case-Control Study

Shape. Start with cases already identified by surveillance: workers with confirmed silicosis linked to engineered stone. For each case, recruit two or three controls who worked in the same shops or similar shops but do not have silicosis on screening. Ask both groups, in the same structured interview, about their cutting methods, ventilation and respirator use over the past ten years, and compare the odds of past dry cutting.

What it would cost in people. Far fewer. The state surveillance program confirmed 243 engineered stone cases from 2019 through 2024 (Flattery et al., 2025), so even a single county is likely to have dozens of eligible cases. Around 60 cases and 150 controls could detect a strong association.

What it would cost in months. Six to nine months: two months to set up, four to six to recruit and interview, one to analyze. Within the board's deadline.

What it would cost in access. Cases are already in contact with the health system and often want to help others avoid their illness. Controls are harder: they must be screened to confirm they are free of disease, and they may worry about their jobs. Recruiting through community organizations and interviewing away from the shop would help.

What it would give. An odds ratio for past dry cutting. It is weaker evidence than a cohort because exposure is recalled after the case knows the diagnosis, which invites recall bias: a worker with silicosis may think harder about the dust than a healthy coworker. Choosing controls from the same shops controls for some shop-level differences but not all.

A Third Measurement the Board Should Not Overlook

Both designs study disease, which lags years behind exposure. The board's decision is about exposure control, and exposure can be measured directly and quickly. Personal air sampling during a work shift in a sample of wet-cutting and dry-cutting shops would show, within weeks, whether workers' breathing-zone silica levels fall below the federal permissible exposure limit of 50 micrograms per cubic meter over an eight-hour day (Occupational Safety and Health Administration, 2016). It would not show disease, but it would answer the question the board can act on: do wet methods bring exposure under the legal limit in our shops?

Protecting Participants in Either Design

Either design would enroll workers whose livelihoods depend on the employers being studied, many without legal immigration status or health insurance. Three protections should be written into the protocol before recruitment. First, no information identifying a worker should be shared with any employer or enforcement agency; results should be reported only by groups of shops. Second, every participant found to have abnormal imaging or lung function must be referred for care at no cost, which in practice means a standing agreement with a public hospital's pulmonary clinic before the first scan. Third, interviews should be offered in Spanish and at times and places away from the shop. These protections cost money and time, and they belong in the comparison, because a study that workers do not trust will not recruit, and one that exposes them to job loss would do harm the county cannot justify. Of the two designs, the case-control study requires these protections for fewer people and for months rather than years.

Recommendation

Run the case-control study, paired with a short air-sampling survey of 20 shops. Together they can be completed within nine months, before the board's deadline. The case-control study gives the board a local estimate of how strongly past dry cutting is associated with disease, and the air sampling shows whether wet methods control exposure in practice. The cohort should be started at the same time, using the screening program already planned, but presented to the board as a long-term evaluation of the program rather than as evidence for the decision. A design that gives the best answer too late is, for this decision, no answer at all.

The recommendation also has a cost the board should hear plainly. The case-control study will produce an odds ratio that some board members will find less convincing than a cohort's rate ratio, and the air sampling may show that some wet-cutting shops still exceed the limit. Both results would still help the decision, and neither should be hidden if it is inconvenient.

References

Fazio, J. C., Garcia, S. R., Torres, I. R., Gandhi, S. A., Cummings, K. J., Buhr, R. G., Riley, K., Ponce, N., Bustamante, A. V., & Glenn, B. (2025). Silica hazards in engineered stone countertop production: Worker experiences and challenges in Los Angeles. American Journal of Industrial Medicine, 68(10), 867-880. https://doi.org/10.1002/ajim.70010

Flattery, J., Woolsey, C., Fazio, J. C., Gandhi, S. A., Heinzerling, A., Harrison, R. J., & Cummings, K. J. (2025). Silicosis surveillance in California, 2019-2024: Tracking an epidemic. American Journal of Public Health, 115(11), 1913-1921. https://doi.org/10.2105/AJPH.2025.308225

Occupational Safety and Health Administration. (2016, March 25). Occupational exposure to respirable crystalline silica. Federal Register, 81, 16286-16890. https://www.federalregister.gov/documents/2016/03/25/2016-04800/occupational-exposure-to-respirable-crystalline-silica